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Live regex tester with multi-flavor compare and click-to-insert cheatsheet.
Reach me at [email protected] or [email protected]. Server is at 62.238.24.63 (production). Visit https://molixa.app/api/health for the canary. Session ID: 8a3e1c0f-91f2-4b7d-a6b2-d6e7f4a3c2b1 Shipped on 2026-05-07. Phone: +1 (415) 555-0100.
A regex tester is a tool that lets you write a regular expression and instantly see what it matches in a sample of text. You can tune your pattern, watch matches highlight live, view every capture group, and try replacements without leaving the page. It is the fastest way to debug a regex before pasting it into your code.
This tester uses the JavaScript regex engine for live matching, then compares your pattern against PCRE, Python, and Go to flag what is portable and what is not. Everything runs in your browser. Your patterns, test text, and replacements stay on your device.
Use it as much as you want. No daily cap, no email signup, no premium gate on features. Regex101's free tier limits saved patterns; we don't.
Most testers only show one regex engine. We tell you which features will break when you port your pattern to Go, Python, or PCRE before you ship.
Your patterns and test text never touch a server. We can't log what we never receive. Compare with regex tools that send every keystroke for "telemetry".
"Invalid regular expression" is useless. We translate native engine errors into specific guidance and point at the exact column where parsing failed.
| Feature | Molixa | Regex101 | RegExr | Debuggex |
|---|---|---|---|---|
| Live highlighting | Yes | Yes | Yes | Yes |
| JS, PCRE, Python, Go compare | Yes | Pick one at a time | JS only | JS, PCRE |
| Common presets | 8+, one click | Library, login required | Yes | No |
| Click-to-insert cheatsheet | Yes | Sidebar reference only | Sidebar reference only | No |
| Free with no signup | Always | Save needs account | Save needs account | Limited |
| Ads on the page | No | Yes | Yes | Yes |
| Browser-only privacy | Yes | Server-side | Server-side | Server-side |
Yes. Unlimited testing, no signup, no daily cap, no ads, no upload limit. The pattern and your test text run entirely in your browser, so we never see your data. Regex101 caps free saves and shows ads; we don't.
Yes. Everything runs in your browser. Your pattern, test text, and any replacements never leave the page. No server logs, no analytics on the input, no storage. Close the tab and the data is gone.
The live engine is JavaScript's native RegExp, which covers most modern syntax including named groups (?<name>...), lookaheads, lookbehinds, and Unicode property escapes. The Compatibility tab compares your pattern against PCRE (PHP), Python re, and Go RE2 and lists what changes you'd need to port it.
Python uses (?P<name>...) for named groups and (?P=name) for backrefs. JavaScript uses (?<name>...) and \k<name>. The Compatibility tab catches this exact case and shows you the rewrite. Paste a Python pattern, click Compatibility, and you'll see the translation.
Yes. Switch to Replace mode and type your replacement string. Back-references like $1, $2, and $<name> work just like in JS String.prototype.replace. The output panel shows the rewritten text, and you can copy or download it as .txt.
Every match in the Matches list expands to show its numbered groups (1, 2, 3...) and named groups. Hover any group to see its position in the source text. Useful for understanding why your pattern matched and which group captured what.
Greedy quantifiers (* + ?) match as much as possible by default. Add ? to make them lazy: *? +? ??. Example: <.*> on '<a><b>' matches the whole string; <.*?> matches '<a>' and '<b>' separately. The cheatsheet has both forms one click away.
Yes for JavaScript (Chrome 62+, Firefox 78+, Safari 16.4+, basically every modern browser). The Compatibility tab will warn you that Go's RE2 engine never supports lookbehind, so if you're targeting Go you'll need a different approach.
The standard six: g (find all matches, on by default in this tester), i (case insensitive), m (^ and $ match line boundaries), s (dot matches newline), u (full Unicode mode for surrogate pairs and property escapes), y (sticky, anchored to lastIndex). Click any flag to toggle it.
Email, URL, IPv4, ISO date (YYYY-MM-DD), international phone, hex color, UUID v4, and credit card. Each preset loads a working pattern, the right flags, and sample text so you can see it match instantly. Use them as starting points and edit to fit your case.
No signup, no daily cap, runs in your browser. Try a preset or paste your own pattern and watch matches highlight live.
Open the regex testerThe Regex Tester page is built, reviewed, and maintained by the Molixa team. We use the tool we ship and update the docs when the behavior changes.